We require the user and their schema to exist, for Oracle -- not just the DB
Oracle users cannot have empty passwords -- enforce this

We provide a user password for other databases as well, as it cannot hurt.
Minimal changes to t/api/group.t to not use principals 1, 2, 3

The original implementation of t/api/group.t blindly stuffed principals
1, 2, and 3 into the groups for membership testing.  These are
(respectively) the RT_System user, the RT_System's ACL equiv group, and
the Everyone group.

Clearly, including the "Everyone" group when testing group membership is
a confounding factor.  Create and use three users, instead.  For minimal
changes, these are $users[1] through $users[3], to line up with the
original '1' through '3'.